Existing flame sensors rely on a phenomenon known as flame rectification to detect the presence of a flame. In such flame sensors, a sensing rod and an electrical ground are positioned in a flame area corresponding to an anticipated location of a flame. The presence of the flame provides an electrically conductive path wherein current may flow. A controller may induce an alternating current on this path. This alternating current is biased by the flame ions, thereby creating a sensible DC offset voltage in the AC signal.
In existing systems, the electrical ground is provided by the flame source, such as an electrically grounded, metal burner. Some burners, such as ceramic burners, are not electrically conductive and cannot serve as an electrical ground. In such installations, a ground rod is positioned proximate the sensing rod. The ground rod has limited surface area, which can result in a failure of a controller to detect the presence of a flame, even when a flame is present.